Subversion Repositories openrisc_2011-10-31

module ram_wb

  (

   // Inputs

   wbm0_adr_i, wbm0_bte_i, wbm0_cti_i, wbm0_cyc_i, wbm0_dat_i, wbm0_sel_i,

   wbm0_stb_i, wbm0_we_i,

   // Outputs

   wbm0_ack_o, wbm0_err_o, wbm0_rty_o, wbm0_dat_o,

   // Inputs

   wbm1_adr_i, wbm1_bte_i, wbm1_cti_i, wbm1_cyc_i, wbm1_dat_i, wbm1_sel_i,

   wbm1_stb_i, wbm1_we_i,

   // Outputs

   wbm1_ack_o, wbm1_err_o, wbm1_rty_o, wbm1_dat_o,

    // Inputs

   wbm2_adr_i, wbm2_bte_i, wbm2_cti_i, wbm2_cyc_i, wbm2_dat_i, wbm2_sel_i,

   wbm2_stb_i, wbm2_we_i,

   // Outputs

   wbm2_ack_o, wbm2_err_o, wbm2_rty_o, wbm2_dat_o,

   // Clock, reset

   wb_clk_i, wb_rst_i

   );

   // Bus parameters

   parameter dw = 32;

   parameter aw = 32;

   // Memory parameters

   parameter mem_size_bytes = 32'h0000_0400; // 1KBytes

   parameter mem_adr_width = 10; //(log2(mem_span));

   input [aw-1:0]        wbm0_adr_i;

   input [1:0]           wbm0_bte_i;

   input [2:0]           wbm0_cti_i;

   input                wbm0_cyc_i;

   input [dw-1:0]        wbm0_dat_i;

   input [3:0]           wbm0_sel_i;

   input                wbm0_stb_i;

   input                wbm0_we_i;

   output               wbm0_ack_o;

   output               wbm0_err_o;

   output               wbm0_rty_o;

   output [dw-1:0]       wbm0_dat_o;

   input [aw-1:0]        wbm1_adr_i;

   input [1:0]           wbm1_bte_i;

   input [2:0]           wbm1_cti_i;

   input                wbm1_cyc_i;

   input [dw-1:0]        wbm1_dat_i;

   input [3:0]           wbm1_sel_i;

   input                wbm1_stb_i;

   input                wbm1_we_i;

   output               wbm1_ack_o;

   output               wbm1_err_o;

   output               wbm1_rty_o;

   output [dw-1:0]       wbm1_dat_o;

   input [aw-1:0]        wbm2_adr_i;

   input [1:0]           wbm2_bte_i;

   input [2:0]           wbm2_cti_i;

   input                wbm2_cyc_i;

   input [dw-1:0]        wbm2_dat_i;

   input [3:0]           wbm2_sel_i;

   input                wbm2_stb_i;

   input                wbm2_we_i;

   output               wbm2_ack_o;

   output               wbm2_err_o;

   output               wbm2_rty_o;

   output [dw-1:0]       wbm2_dat_o;

   input                wb_clk_i;

   input                wb_rst_i;

   // Internal wires to actual RAM

   wire [aw-1:0]         wbs_ram_adr_i;

   wire [1:0]            wbs_ram_bte_i;

   wire [2:0]            wbs_ram_cti_i;

   wire                 wbs_ram_cyc_i;

   wire [dw-1:0]         wbs_ram_dat_i;

   wire [3:0]            wbs_ram_sel_i;

   wire                 wbs_ram_stb_i;

   wire                 wbs_ram_we_i;

   wire                 wbs_ram_ack_o;

   wire                 wbs_ram_err_o;

   wire                 wbs_ram_rty_o;

   wire [dw-1:0]         wbs_ram_dat_o;

   reg [2:0]             input_select, last_selected;

   wire                 arb_for_wbm0, arb_for_wbm1, arb_for_wbm2;

   // Wires allowing selection of new input

   assign arb_for_wbm0 = (last_selected[1] | last_selected[2] |

                          !wbm1_cyc_i | !wbm2_cyc_i) & !(|input_select);

   assign arb_for_wbm1 = (last_selected[0] | last_selected[2] |

                          !wbm0_cyc_i | !wbm2_cyc_i) & !(|input_select);

   assign arb_for_wbm2 = (last_selected[0] | last_selected[1] |

                          !wbm0_cyc_i | !wbm1_cyc_i) & !(|input_select);

   // Master select logic

   always @(posedge wb_clk_i)

     if (wb_rst_i)

       input_select <= 0;

     else if ((input_select[0] & !wbm0_cyc_i) | (input_select[1] & !wbm1_cyc_i)

              | (input_select[2] & !wbm2_cyc_i))

       input_select <= 0;

     else if (!(&input_select) & wbm0_cyc_i & arb_for_wbm0)

       input_select <= 3'b001;

     else if (!(&input_select) & wbm1_cyc_i & arb_for_wbm1)

       input_select <= 3'b010;

     else if (!(&input_select) & wbm2_cyc_i & arb_for_wbm2)

       input_select <= 3'b100;

   always @(posedge wb_clk_i)

     if (wb_rst_i)

       last_selected <= 0;

     else if (!(&input_select) & wbm0_cyc_i & arb_for_wbm0)

       last_selected <= 3'b001;

     else if (!(&input_select) & wbm1_cyc_i & arb_for_wbm1)

       last_selected <= 3'b010;

     else if (!(&input_select) & wbm2_cyc_i & arb_for_wbm2)

       last_selected <= 3'b100;

      // Mux input signals to RAM (default to wbm0)

   assign wbs_ram_adr_i = (input_select[2]) ? wbm2_adr_i :

                            (input_select[1]) ? wbm1_adr_i :

                            (input_select[0]) ? wbm0_adr_i : 0;

   assign wbs_ram_bte_i = (input_select[2]) ? wbm2_bte_i :

                            (input_select[1]) ? wbm1_bte_i :

                            (input_select[0]) ? wbm0_bte_i : 0;

   assign wbs_ram_cti_i = (input_select[2]) ? wbm2_cti_i :

                            (input_select[1]) ? wbm1_cti_i :

                            (input_select[0]) ? wbm0_cti_i : 0;

   assign wbs_ram_cyc_i = (input_select[2]) ? wbm2_cyc_i :

                            (input_select[1]) ? wbm1_cyc_i :

                            (input_select[0]) ? wbm0_cyc_i : 0;

   assign wbs_ram_dat_i = (input_select[2]) ? wbm2_dat_i :

                            (input_select[1]) ? wbm1_dat_i :

                            (input_select[0]) ? wbm0_dat_i : 0;

   assign wbs_ram_sel_i = (input_select[2]) ? wbm2_sel_i :

                            (input_select[1]) ? wbm1_sel_i :

                            (input_select[0]) ? wbm0_sel_i : 0;

   assign wbs_ram_stb_i = (input_select[2]) ? wbm2_stb_i :

                            (input_select[1]) ? wbm1_stb_i :

                            (input_select[0]) ? wbm0_stb_i : 0;

   assign wbs_ram_we_i  = (input_select[2]) ? wbm2_we_i  :

                            (input_select[1]) ? wbm1_we_i  :

                            (input_select[0]) ? wbm0_we_i : 0;

   // Output from RAM, gate the ACK, ERR, RTY signals appropriately

   assign wbm0_dat_o = wbs_ram_dat_o;

   assign wbm0_ack_o = wbs_ram_ack_o & input_select[0];

   assign wbm0_err_o = wbs_ram_err_o & input_select[0];

   assign wbm0_rty_o = 0;

   assign wbm1_dat_o = wbs_ram_dat_o;

   assign wbm1_ack_o = wbs_ram_ack_o & input_select[1];

   assign wbm1_err_o = wbs_ram_err_o & input_select[1];

   assign wbm1_rty_o = 0;

   assign wbm2_dat_o = wbs_ram_dat_o;

   assign wbm2_ack_o = wbs_ram_ack_o & input_select[2];

   assign wbm2_err_o = wbs_ram_err_o & input_select[2];

   assign wbm2_rty_o = 0;

   ram_wb_b3 ram_wb_b3_0

     (

      // Outputs

      .wb_ack_o                         (wbs_ram_ack_o),

      .wb_err_o                         (wbs_ram_err_o),

      .wb_rty_o                         (wbs_ram_rty_o),

      .wb_dat_o                         (wbs_ram_dat_o),

      // Inputs

      .wb_adr_i                         (wbs_ram_adr_i),

      .wb_bte_i                         (wbs_ram_bte_i),

      .wb_cti_i                         (wbs_ram_cti_i),

      .wb_cyc_i                         (wbs_ram_cyc_i),

      .wb_dat_i                         (wbs_ram_dat_i),

      .wb_sel_i                         (wbs_ram_sel_i),

      .wb_stb_i                         (wbs_ram_stb_i),

      .wb_we_i                          (wbs_ram_we_i),

      .wb_clk_i                         (wb_clk_i),

      .wb_rst_i                         (wb_rst_i));

   defparam ram_wb_b3_0.aw = aw;

   defparam ram_wb_b3_0.dw = dw;

   defparam ram_wb_b3_0.mem_size_bytes = mem_size_bytes;

   defparam ram_wb_b3_0.mem_adr_width = mem_adr_width;

endmodule // ram_wb